Mini Cafe Racer, Board Tracker, Motorized Bicycle, Frankenstein Machine

Let me preface this by saying that this is NOT a step by step guide. I realize that the point of this site is to post and find instructions on how to build and make incredible things and I am deviating from that purpose, so I apologize, I'm bad. However, I recently built this little moped/cafe racer/board tracker thing, and I wanted to share it with the world in hopes that it might help someone looking to do something similar. That being said, I did not have many in progress pictures to share and most of them were taken after the described process already took place. Also, there are people who are far more skilled and dedicated than I am who have already written guides on this very type of project, and I actually used some of theirs as inspiration for mine, so I will give them due credit and post links for their guides throughout the steps along with links for my other sources at the end. All that notwithstanding, I had a great time on this little build and I hope it can serve as inspiration for somebody else.

I had this old bicycle that I used to ride when I was ten or so. I'd been slowly picking parts off of it to repair mine and my wife's bikes that we ride regularly. Eventually, I looked at it and realized that all I had left was a bicycle frame, two wheels that didn't match and weren't even bolted on, pedals, a chain, and functioning brake levers with no pads. I looked at it and thought to myself, as I am prone to do, "what could I build out of this?"

I looked around at some different ideas. I considered building a gravity bike which, by the way, there is an awesome guide for here, but I live in the Midwest and big hills are hard to come by. I thought about fitting an electric motor and making an ebike, but electric motors get pricey really quick, don't move very fast, and aren't all that efficient. Eventually, though, I discovered gasoline bicycle engines which, I realize, will be an abomination to some, but they are pretty fun and are supposed to be pretty efficient. They only cost $100-150, they move at about 30-40 mph which is plenty fast, and they supposedly get around 100 miles to the gallon. Sold.

The idea was to create a feasible mode of transportation that could reliably carry a rider from point A to point B while still looking at least fairly cool. The second idea was to do it for under $200.

This turned out to be a really fun little summer project and the end result was really satisfying. It's a blast to ride, and, if I lived in town, I wouldn't hesitate to use it as around town transportation.

And now, without further ado: my tiny machine.

As usual, I take no responsibility for any harm you cause to yourself, someone else, your own property, someone else's property, or any other harm you may cause under the sun. If you do a build like this one, you will be making a motor vehicle. Please make sure that everything is bolted solid, installed according to the manual, and perfectly safe and secure before you start riding. Also, make sure to check with local law enforcement about legal considerations before riding around town.

The first thing you need to do is select a bicycle to start with as a base. The one I had on hand was a 24" men's bike with a tube frame. The 24" frame and wheels are a little small for my 6'6" frame if I had to pedal it much, but it works well for this project. I also liked the proportion of the wheels and frame to the motor and the rest of the parts, so it was a happy coincidence. Whatever size you choose, make sure your motor can fit inside the frame. Most brands advertise that they fit in bikes no smaller than 24". Also, it is apparently possible to mount the motor on a non-tubular frame, but I have no idea how, so I recommend sticking with an older style tube frame.

Once you have your motor on hand, check to make sure it will fit your bicycle. I fully installed mine and took it for a test run to make sure it worked and because it was fun. This really helped me find problem areas in the build, such as the rear wheel being warped and rubbing against the chain and the need for a two into one brake lever among other things. It's not necessary to piece it all together first, but it did help me through the process.

Easier said than done, but necessary if you want to make it completely your own. If you're content with the color and/or styling that your bicycle already has, then skip this step, but if you want to paint it, it will be much easier if it's in pieces than if it's all together. Keep in mind, if you want to fully customize, you will need to remove the handlebars, handlebar stem, front forks, front and rear wheels, pedals and pedal stems, brake systems, shifting levers and cables (if they're present), and the chain (I just used a hammer and a punch, but a chain breaking tool would have been easier). If you are removing decals, a good method is to take a hair dryer and heat them up for a while before pulling them off. This warms up the glue, making it easier to peel them off. I got impatient with mine and left residue behind which is part of why I wound up accenting with the textured paint.

Once you have it a stripped down, take a your primer and give anything you're painting a few coats. Work in light layers and be patient or you'll wind up with drips. It took me probably three or four passes with the primer before I was satisfied. After the primer dries, start in with your top coat. Again, moving slowly and with light coats. I wound up giving five or six coats to all my parts to make sure they were nice and smooth. After the top coat is on and dry, tape and mask off the areas that you don't want getting accented and spray them with your accent color. After the accent color dries, peel off your tape and start in with the clear coat. Five or six light coats of clear and, voilà, fresh paint job. I went ahead and painted the gas tank and handlebars with my accent color too, though they didn't really need it. It just helped tie the whole bike together.

Both of my wheels were warped so I needed to get them trued. I followed this instructable to figure it out. Also, I wanted to switch from a typical mountain bike gear setup to a single speed, so I ordered a thread on single speed cassette and had it installed at the local bike shop. You can do this yourself with a specialized tool, but the shop did it for free so it was worth it to not buy a tool I would only use once. I also had to rework the braking from a typical two handed system to a single handed one. Since I already had it apart, I went ahead and greased all the bearings in the handlebar stem, the pedal stems, and the rear wheel, just to make things a little smoother. I also replaced my tires and inner tubes, brake pads, and removed the paint from my front wheel.

The manual that comes with the bike is fairly clear on how to install the motor, and there's a great instructable on it that can be found here already so I won't bore you with the details, but the next thing you need to do is get your motor installed and tweaked. A few tips from my experience: it's possible to adjust the way the chain to the engine travels by readjusting where the back wheel sits. My chain was still rubbing the tire slightly even though it was trued, so I fiddled with the positioning and it worked great. The more slack you have in your cables, the less responsive the throttle and clutch will be so try to get rid of as much slack as you can by routing the cables under other parts and around the frame. Play with the idle adjustment and get it working or the engine will die every time you stop which is really bad for the internal parts. Make sure everything is TIGHT and possibly consider using a thread locker to make sure things stay put. Also, my frame was slightly smaller than the brackets on the motor, so I used several strips of old inner tube to beef up the frame.

If you decide you want to replace your seat with a hand made one, then you'll obviously have some more work to do. I went this route, but if my starting bike had been a beach cruiser style or had had more of a vintage look, I probably would have kept the original, wide seat. You could also do something similar to what I did if you had a banana seat but I was trying to save money and this was cheap.

I mocked up what I thought I wanted with cardboard. I wound up changing the design slightly, but it was good to get to look at the mock-up first because it helped me to see what I didn't like. I disassembled the old bike seat and used the stem to help support my new one. I cut three pieces of wood to size, in this case two pieces of oak and a piece of walnut. I glued and pinned them together, then I used a saber saw to cut them to shape and a sander to smooth out the edges and sides. I drilled a hole partially through the seat at the angle I needed for the stem to sit happily, cut a small slit in the front so the seat and gas tank would fit together nicely, and drilled two more holes in the back for the bracket I was making. Then I used a few coats of polyurethane spray, sanding between coats, to finish it up.

After I got the seat made, I took my steel and heated it up to form it to shape. I did this on a forge, but you could probably use a torch as well. After it was shaped, I quenched it in water and then drilled holes on top to mount the seat and on the sides to slip them over the wheel axles. I removed the rear wheel, put the bracket over the axles, slid the seat down on the stem, and then bolted the bracket to the seat with a small steel support between the bracket and the wood to keep the seat from cracking.

This is another completely optional step, but it really added to the overall look and feel of the bike. I'm not really sure that the headlight is bright enough to be able to see the road after dark, but it works at least as well as a reflector for alerting cars to your presence. To install it, I took the old front reflector, popped it off its bracket, and bolted the headlight on in its place with a couple nuts and a lock washer. Different headlights mount differently, but this one worked great like this. The brake light is a Sigma Sport light that just clips right on to the brake cable. It took some adjustment to get to work just right, but it is very bright.

At this point I thought I was done, but I neglected to think about how incredibly uncomfortable it would be to ride around on a motorized bicycle with a wooden seat and no shock absorption. I decided to add a pad. I took some vinyl that I had laying around and cut a rectangle about 10" x 18". then I took some stuffing, that I also had lying around, and put a generous amount in the vinyl. I then proceeded to make a little vinyl burrito, folding the two sides over to the middle and then the other two sides together to keep the stuffing in. I set it on the bike seat, and tied it down with leather cord. I later replaced the cord with an old belt which I think looks much better and I know works much better.

Inevitably, there will be things you run across that need to happen to make this a truly viable machine. For me, it took the form of paint touch up, motor adjustment and replacement of some of the rubber pieces I used to help mount the engine, motor adjustment, adjustment of both the pedal and motor chains, brake adjustment, clutch adjustment, throttle adjustment, and simple tweaking of the carb, fuel delivery, and exhaust positioning. You will most likely deal with completely different things, so check out the links at the end for some forums and sites that helped me figure things out.

And that's it. This thing is a blast to ride! It hits 30-35 mph on the road which may not seem like much, but is very fast for a bicycle. If you decide you want to build one, please be careful. I'm honestly not sure if it is technically road legal or not. I am planning on checking with the local sheriff if I ever decide to ride it as more than just a toy on back country roads. I would strongly encourage you to do the same if you are planning on building one. Also note that the motor on this little machine is pretty noisy, about the level of a weed whacker, so be considerate of other people and don't rev it up in the middle of the night or near the library or anything of the sort. Like I said before, I've included sources of help and inspiration for me during this build at the end. Hopefully they can help you out too. Thanks for reading! I hope you have fun with your build!

Instructables (of course)

Motored Bikes

This Man's Impressive Build

Kneeslider

Kneeslider

And Kneeslider

Moto USA

Imperial Cycles

Sheldon Brown

Obviously some of these served as practical help and others just served as inspiration. I'll leave you to figure out which are which